Custom MCP Environment Variable Bypass in Flowise by FlowiseAI

CVE-2026-58057

What is CVE-2026-58057?

Flowise versions prior to 3.1.3 suffer from a vulnerability due to improper validation of Custom MCP standard input/output environment variables against a denylist. The case-sensitive nature of the comparison allows an authenticated user to exploit this flaw on Windows systems where environment variables are case-insensitive. By supplying 'node_options', an attacker can bypass the NODE_OPTIONS entry in the denylist. This enables the execution of arbitrary code within the Flowise server context, posing a significant security risk.

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